Medical imaging devices are often used to image moving organs. Cardiac image processing devices, in particular, are always used to image moving organs, either the heart (via ultrasound imaging for example), or the coronaries (via angiography for example). Many of these imaging processing devices are used to quantify the motion either as an indication by itself or as part of an image-processing algorithm.
An image processing device for Left Ventricle Analysis is used to evaluate Ejection Fraction, which is the percentage of the blood pumped out during each heartbeat. Left Ventricle Analysis involves computing the Left Ventricle volume from an angiogram (taken from a cine-angio sequence of images). The Left Ventricle volume is computed once for the heart in its systolic phase and once for the heart in its diastolic phase. Ejection Fraction is estimated from the ratio of these volumes. Identifying the systolic and diastolic images is part of the LVA procedure.
Myocardium thickness and Heart Wall Motion are evaluated from Ultrasound Images to indicate heart failure conditions. Both procedures, again, involve the identification of systolic and diastolic instances. Furthermore, quantifying the object's motion could be directly used for Wall Motion evaluation.
Intra-Vascular Ultrasound (IVUS) is a method of evaluating and analyzing coronary defects by means of inserting an intra-vascular ultrasound device and imaging the vessel. IVUS measurements include measurements of the luminal vessel area. Estimation of the luminal area very much depends on the heart phase and results vary for different images depicting different stages within the cardiac cycle. Again, it is useful to identify the diastolic—or the minimal movement instance—in order to perform measurements on the optimal image.
CT, MRI and PET are also used to image the heart as well as the coronary arteries. These methods use ECG triggering that synchronize image acquisition to ECG events (for example end diastole) in order to decrease motion artifacts that decrease image resolution and image quality, thus impairing the image result and consequently clinical assessments.
In the field of medical imaging, angiography is a gold standard for cardio-vascular diagnostics. Conventional (2D) angiography, produced by C-Arm X-ray equipment, applied during a catheterization procedure, provides a most accurate modality for evaluating vessel disease. Quantitative Coronary analysis is often applied to measure vessel disease. Analysis is applied to a certain angiogram to measure vessel dimensions; the results are different, when derived from different angiograms, depicting the vessel in different instances of the heart cycle; QCA procedure recommends the use of the end-diastole image.
Three-Dimensional reconstruction of coronary vessels is also a method of evaluating vessel disease from a procedure of conventional angiography. While it is well known and widely covered in the literature that 2D angiography has some inherent drawbacks, mainly presenting and measuring projected objects, which result in inaccurate measurements, methods are available for performing three-dimensional reconstruction of the arteries from the series of the two-dimensional images obtained. In order to reconstruct a three-dimensional image of the arteries, it is necessary to obtain at least two two-dimensional images of the arteries in the same phase of the heartbeat, for example at diastole. Therefore, image acquisition is usually synchronized to an E.C.G signal. This procedure involves simultaneous recordings of the video signal from the X-ray camera and the patient's E.C.G signal. This procedure of ECG gating suffers from many drawbacks. For example, the ECG signal, in many cases, is hard to correlate to a desired state of the coronaries. Furthermore, when reviewing recorded angiographic films, often the E.C.G signal is unavailable.
There are many additional cardiac and other medical procedures and measurements that involve identifying instances within the object's movement cycle and also involve quantifying this movement.
Thus, it is desirable to quantify the organ movements. It is desirable to identify instances within the movement cycle. It is also evident that imaging a moving organ poses great difficulties for all modalities, impairing quantitative results and clinical assessment.